水晶體與人工水晶體之力學分析

Abstract

本研究探討水晶體在調視過程中的力學特性，發展了一種模擬生物眼球力學特徵的實驗方法，並研究懸韌帶作為力傳導介質的作用。實驗設計包括豬水晶體之拉伸試驗，懸韌帶與水晶體的黏著方式，光彈應力分析下觀察等差線分佈。然而，在平面偏振光學系統下未觀察到顯著的等差線，為水晶體內部應力分佈過於均勻或折射率差異不足以產生顯著雙折射效應。為深入研究，我們嘗試改變施力方向和位置，並引入圓偏振光學系統以消除等傾線干擾，即便如此，豬水晶體仍未顯示可觀測的等差線。這表明水晶體的應力分佈或材料特性可能導致光在其內部產生的相位差不足以形成可見的等差線。此外我們考慮了水晶體外層囊袋的光彈性行為。囊袋由膠原蛋白組成，具備一定彈性，類似於角膜的層狀纖維排列。如果施加足夠外力於囊袋就可能顯示出等差線。 光彈性技術在水晶體分析中受限，我們進行了有限元素法分析與影線處理。建立了豬水晶體的三維有限元素模型，並使用實驗中測得的外力作為邊界條件進行模擬與比較。有限元素法結果與影像處理結果一致表明有限元素分析和影像處理結果相符。 在人工水晶體研究中，我們設計了沖壓模具以製造成本低且生產效率高的人工水晶體，並製作了人工囊袋以模擬其在囊袋中的狀態。模擬調視拉伸實驗顯示，人工水晶體在人工囊袋內的光彈等差條紋在不同應力下光強度變化。應力變化對等色線亮度改變證實了應力差異的存在。

This study investigates the mechanical properties of the lens during accommodation, developing an experimental method to simulate the biomechanical characteristics of the eye and exploring the role of zonules as a force transmission medium. The experimental design includes tensile tests on porcine lenses to observe the adhesion between the zonules and the lens, and analyzes the distribution of isochromatic lines under photoelastic stress. However, no significant isochromatic lines were observed under a plane-polarized optical system, likely due to a uniform stress distribution within the lens or insufficient refractive index differences to produce significant birefringence effects. To further investigate, we attempted to alter the direction and position of the applied force and introduced a circularly polarized optical system to eliminate isoclinic line interference. Even with these adjustments, the porcine lens did not display observable isochromatic lines, suggesting that the stress distribution or material properties of the lens might prevent sufficient phase differences in light within the lens to form visible isochromatic lines. Additionally, we considered the photoelastic behavior of the outer capsular bag of the lens, which is composed of collagen and exhibits some elasticity similar to the layered fiber arrangement of the cornea. If sufficient external force is applied, the capsular bag may display isochromatic lines. Although the application of photoelastic techniques in lens analysis is limited, we conducted finite element method (FEM) analysis and image processing. A 3D finite element model of the porcine lens was established, and the forces measured in the experiment were used as boundary conditions for simulation and comparison. The FEM results were consistent with image processing outcomes, indicating agreement between FEM analysis and image processing results. In the study of intraocular lenses, we designed stamping molds to produce cost-effective and highly efficient IOLs, and created an artificial capsular bag to simulate the state of the lens within the capsular bag. Simulated accommodation stretching experiments showed that the photoelastic isochromatic fringes of the IOL within the artificial capsular bag exhibited changes in light intensity under different stress conditions. The change in light intensity of the isochromatic lines due to stress variations confirmed the existence of stress differences.